* broken.
*/
if (TransactionIdIsValid(prev_xmax) &&
- !TransactionIdEquals(prev_xmax,
- HeapTupleHeaderGetXmin(heapTuple->t_data)))
+ !HeapTupleUpdateXmaxMatchesXmin(prev_xmax, heapTuple->t_data))
break;
/*
* tuple. Check for XMIN match.
*/
if (TransactionIdIsValid(priorXmax) &&
- !TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(tp.t_data)))
+ !HeapTupleUpdateXmaxMatchesXmin(priorXmax, tp.t_data))
{
UnlockReleaseBuffer(buffer);
break;
} /* end of loop */
}
+/*
+ * HeapTupleUpdateXmaxMatchesXmin - verify update chain xmax/xmin lineage
+ *
+ * Given the new version of a tuple after some update, verify whether the
+ * given Xmax (corresponding to the previous version) matches the tuple's
+ * Xmin, taking into account that the Xmin might have been frozen after the
+ * update.
+ */
+bool
+HeapTupleUpdateXmaxMatchesXmin(TransactionId xmax, HeapTupleHeader htup)
+{
+ TransactionId xmin = HeapTupleHeaderGetXmin(htup);
+
+ /*
+ * If the xmax of the old tuple is identical to the xmin of the new one,
+ * it's a match.
+ */
+ if (TransactionIdEquals(xmax, xmin))
+ return true;
+
+ /*
+ * If the Xmin that was in effect prior to a freeze matches the Xmax,
+ * it's good too.
+ */
+ if (HeapTupleHeaderXminFrozen(htup) &&
+ TransactionIdEquals(HeapTupleHeaderGetRawXmin(htup), xmax))
+ return true;
+
+ /*
+ * When a tuple is frozen, the original Xmin is lost, but we know it's a
+ * committed transaction. So unless the Xmax is InvalidXid, we don't know
+ * for certain that there is a match, but there may be one; and we must
+ * return true so that a HOT chain that is half-frozen can be walked
+ * correctly.
+ *
+ * We no longer freeze tuples this way, but we must keep this in order to
+ * interpret pre-pg_upgrade pages correctly.
+ */
+ if (TransactionIdEquals(xmin, FrozenTransactionId) &&
+ TransactionIdIsValid(xmax))
+ return true;
+
+ return false;
+}
/*
* UpdateXmaxHintBits - update tuple hint bits after xmax transaction ends
* end of the chain, we're done, so return success.
*/
if (TransactionIdIsValid(priorXmax) &&
- !TransactionIdEquals(HeapTupleHeaderGetXmin(mytup.t_data),
- priorXmax))
+ !HeapTupleUpdateXmaxMatchesXmin(priorXmax, mytup.t_data))
{
result = HeapTupleMayBeUpdated;
goto out_locked;
* Check the tuple XMIN against prior XMAX, if any
*/
if (TransactionIdIsValid(priorXmax) &&
- !TransactionIdEquals(HeapTupleHeaderGetXmin(htup), priorXmax))
+ !HeapTupleUpdateXmaxMatchesXmin(priorXmax, htup))
break;
/*
htup = (HeapTupleHeader) PageGetItem(page, lp);
if (TransactionIdIsValid(priorXmax) &&
- !TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(htup)))
+ !HeapTupleUpdateXmaxMatchesXmin(priorXmax, htup))
break;
/* Remember the root line pointer for this item */
* atomic, and Xmin never changes in an existing tuple, except to
* invalid or frozen, and neither of those can match priorXmax.)
*/
- if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
- priorXmax))
+ if (!HeapTupleUpdateXmaxMatchesXmin(priorXmax, tuple.t_data))
{
ReleaseBuffer(buffer);
return NULL;
/*
* As above, if xmin isn't what we're expecting, do nothing.
*/
- if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
- priorXmax))
+ if (!HeapTupleUpdateXmaxMatchesXmin(priorXmax, tuple.t_data))
{
ReleaseBuffer(buffer);
return NULL;